JPH0253092B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a stabilizer, and more particularly to a method for producing a polymer that can be used as a dispersant for bentonite used in the stabilizer. Stabilizing liquid is a liquid used to fill the excavated space during soil layer excavation in boring, continuous wall construction methods, etc., to prevent the collapse of the soil layer wall by increasing the internal pressure, and to retain the mixed earth and sand in the liquid. It is a general term for CMC, which has traditionally been used as a dispersant for bentonite, is a natural product that rapidly loses its effectiveness due to spoilage as a result of being decomposed by microorganisms. Even if CMC was added to the spoiled muddy water, it would decompose immediately and the effect could not be restored, so the only option was to throw away the spoiled muddy water. To prevent this, it is desirable to prepare the stabilizer with a synthetic material that is not subject to microbial decomposition, such as a water-soluble acrylic polymer. As mentioned above, a dispersant using a stabilizing liquid must have a thickening effect in order to retain earth and sand in the liquid. However, commercially available water-soluble acrylic polymers cannot be used as dispersants because they have the property of agglomerating earth and sand mixed into the liquid. Also, very low molecular weight acrylic polymers do not exhibit a flocculating effect, but they do not have a thickening effect, so a stabilizing solution cannot be used. The properties of such conventional water-soluble polymers depend on the polymerization conditions and are common to polymers produced using redox or azo catalysts. As a result of various studies on such conditions, the present inventor discovered that it is possible to produce a dispersant with a thickening effect that can be used in stabilized liquids by polymerizing using a reducing agent and an azo catalyst together, and has developed the present invention. Reached. Although the reason why the polymer in the present invention is specifically effective is unknown, it is thought to be due to the molecular structure of the polymer. The water-soluble acrylic polymer used in the present invention has a composition in which the molar ratio of (meth)acrylic acid and (meth)acrylamide is 100:0 to 50:50, and 60% or more of the acrylic acid is amine, ammonium, or alkali metal. It is preferable that the acrylic acid is in the form of an acrylate that has been neutralized by the acrylate. As a catalyst for initiating polymerization, azo catalysts such as azobisisobutyronitrile, azobisisocyanovaleric acid, and azobisaminodinopropane are suitable; persulfates, hydrogen peroxide, and organic peroxides are not suitable.
Sulfites and hydrogen sulfites are most preferred as reducing agents. Nithionite and thiosulfate have poor performance, and heavy metal ions such as ferrous sulfate are ineffective. These reducing agents are added in an amount greater than enough to consume all of the dissolved oxygen in the monomer, and are usually selected to provide a desired viscosity in the range of 50 to 50,000 ppm relative to the monomer solution. The concentration of the monomer solution during polymerization is important, and by adjusting the water content to 40 to 60% by weight of the acrylic monomer, the water can be vaporized by the heat of polymerization, and it can be pulverized into a fine powder without going through a drying process after polymerization. You can get it. The solubility can also be improved by mixing an alkali metal salt such as soda carbonate with the obtained powder. The polymerization container must be open at the top to allow water vapor to diffuse and diffuse, and polymerization on an endless belt gives good results. The present invention will be specifically explained below using Examples. Example 1 Add 35 g of 30% ammonia water to 72 g of acrylic acid at 30°C.
Prepare the monomer solution by mixing while cooling.
After mixing a solution of 0.7 g of AIBN dissolved in 7 ml of acetone, 2 g of sodium bisulfite was added to 8 ml of ammonia water.
Immediately after adding and mixing the solution dissolved in 10 g, polymerization was carried out in a Teflon-coated shallow dish to obtain a polymer dry solid having a drying loss of 9%. After pulverization, the viscosity at 25℃ was measured using a rotational viscometer after dissolving the polymer in 1N saline solution at a concentration of 1%.
It was 8.5 cp. Let the powder be Sample 1. Comparative example 1 72g of acrylic acid and 43g of 30% ammonia water at 30℃
Adjust the mixed monomer solution while cooling to
Immediately after mixing, a solution of 0.7 g of AIBN and 0.07 g of dodecyl mercaptan dissolved in 7 ml of acetone was transferred to a Teflon shallow dish and polymerized to obtain a dry polymer solid having a loss on drying of 9% and a viscosity of a 1% solution in 1N saline of 8.7 cp. This powder is designated as sample 2. Example 2 A solution prepared by dissolving 0.7 g of azobisamidinopropane hydrochloride and 7 mg of sodium bisulfite in 4 g of water was added to a mixed solution of 28 g of acrylamide, 11 g of acrylic acid, 50 g of potassium acrylate, and 26 g of water. Immediately after mixing, the mixture was placed in a Teflon-coated shallow dish. The polymer was transferred and polymerized to obtain a dry polymer solid having a loss on drying of 9.5% and a viscosity of a 1% solution in 1N saline of 8.5 cp. This powder is designated as sample 3. Comparative Example 2 Polymerization was carried out under the same conditions as in Example 2 except that sodium hydrogen sulfite was not added, and the drying loss was
A 9.5% polymer dry solid was obtained with a 1% solution viscosity of 9.7 cp in 1N saline. This powder is designated as sample 4. Effect test 42g of bentonite was added to 700ml of tap water while stirring in a mixer, and after 3 minutes, a 2% aqueous dispersant solution was added.
Add 10ml and continue stirring for a further 5 minutes. After standing overnight, the mixture was stirred with a stirrer for 5 minutes, and the funnel viscosity and water amount were measured. Funnel viscosity was measured in seconds using a Funnel viscometer (500 ml/500 ml), and the amount of water was measured in ml at 3 kg/cm ² for 30 minutes using an API standard over-testing machine. 【table】

Claims (1)

[Claims] 1 The molar ratio of acrylic acid and acrylamide is
100:0 to 50:50 and 60% of acrylic acid
The above is in the form of an acrylate, and an azo catalyst is added to a monomer aqueous solution with a water content of 40 to 60% by weight based on the total acrylic monomer and polymerized, and the water is evaporated by the heat of polymerization to form a dry solid. 1. A method for producing a dispersant for stabilizing liquid preparation, which comprises adding 50 to 50,000 ppm of a reducing agent to a monomer solution and dissolving the produced polymer in water.